1. Technical Field
The present disclosure relates to a method of separating carbon nanotubes.
2. Description of the Related Art
The carbon nanotube (CNT) is a compound in which carbon atoms are bonded to each other in a hexagonal, honeycomb pattern to form a tube shape. Carbon nanotubes have very high anisotropy and have various structures such as single-walled, multi-walled, and bundled structures. Carbon nanotubes are nanomaterials on the scale of nanometers (nm=one billionth of a meter) and exhibit superior mechanical properties, electrical selectivity, excellent field-emission properties, and highly efficient hydrogen storage properties.
Furthermore, carbon nanotubes exhibit characteristics of a semiconductor or metal depending on how the hexagonal honeycomb of carbon atoms is arranged (rolled). The energy gap of the carbon nanotube varies according to the diameter of the tube, and the quasi-one-dimensional energy structure of the carbon nanotube allows the carbon nanotube to have unusual quantum effects.
Carbon nanotubes can be synthesized by various methods such as arc discharge, pyrolysis, laser ablation, plasma enhanced chemical vapor deposition (PECVD), thermal chemical vapor deposition, and electrolysis. At the stage of synthesis, carbon nanotubes exist mostly in the form of bundles. Therefore, to fully utilize superior mechanical and electrical properties of carbon nanotubes, it is important to separate and disperse the carbon nanotubes one by one. Moreover, carbon nanotubes exist as a mixture of carbon nanotubes with metallic characteristics and carbon nanotubes with semiconducting characteristics. Therefore, it is desirable to isolate different carbon nanotubes that serve different purposes. For example, only metallic carbon nanotubes are used for an electrode to increase the conductivity of the electrode. In addition, only semiconducting carbon nanotubes are used for the semiconductor layer of a transistor. In this regard, various studies are being conducted to efficiently separate carbon nanotubes with desired characteristics from other carbon nanotubes.